Gordon Brown is planning a special Cabinet meeting outside London as he seeks to mount a fightback against questions over his leadership.

However, the Prime Minister's supporters are likely to warn that the meeting, set for the West Midlands on September 8, could come too late to save him amid warnings he may face a leadership challenge before the end of this month.

Mr Brown, who is due to follow his holiday in Suffolk with a visit to the Olympics in Beijing, has been told to reconsider his travel plans amid fears that rivals could try to strike while he is out of the country.

He is also planning that during their stay in the West Midlands, ministers will take part in a series of events designed to help them "engage" with the public.

Cabinet meetings are normally held on a Tuesday morning in No 10 but a Downing Street spokesman said it was hoped that in future more would take place away from the capital.

"We feel that it is consistent with the Government's approach that it wants to listen and learn from the experiences of people in this country," a Downing Street spokesman said.

It was also announced that Chancellor Alistair Darling was taking over responsibility for coordinating Government activity in London this week while the Prime Minister continues his family holiday in Suffolk.

The first plans for a fightback were announced after the row over the Prime Minister's future was reignited by a leaked memo from Tony Blair describing Mr Brown's leadership as "vacuous".

Mr Blair told allies that Mr Brown has made "fatal" and "lamentable" errors and played into David Cameron's hands by "dissing" New Labour's own record in an attempt to distance himself from his predecessor.

The memo's release came as Stephen Byers, a Blairite former cabinet minister, openly backed David Miliband's call for Labour to "renew" itself, an appeal that some see as a tacit call for a change of leadership.

Mr Byers wrote that Labour had "a mountain to climb" in order to win the next general election, but that under Mr Brown were only coming up with "a multitude of small policies and worthy initiatives that are more suited to a Sunday afternoon stroll".

Mr Blair's memo to his inner circle, which was drawn up last autumn, was disclosed on Sunday, days after Mr Miliband, the Foreign Secretary, also a Blairite, openly positioned himself as a rival to Mr Brown.

By disowning the New Labour agenda, the former prime minister wrote, Mr Brown has forfeited the chance of a fourth general election win.

Despite concerns of a Blairite plot, however, there is no sign that Downing Street will alter Mr Brown's travel plans, not least to avoid the appearance of panic.

Mr Blair has always publicly insisted he is loyal to Mr Brown, but some of Mr Brown's allies now fear that Mr Blair and his supporters could overshadow his successor much as Margaret Thatcher did to Sir John Major.

The timing of the leak has triggered speculation that the former prime minister and his allies are now mounting a campaign to undermine his successor.

"It's like boiling a frog," said one minister. "You slowly increase the heat until it becomes impossible to survive."

A number of former ministers, including Mr Byers and Charles Clarke, the former Home Secretary, are now thought to be preparing a series of statements and policy proposals. Working alongside other party figures, they are thought to have a view to releasing them gradually over the next few weeks.

Some MPs expect the pressure on Mr Brown to culminate in an outright challenge to his position next month, in the weeks before Labour's annual conference in Manchester starting on September 20.

Trying to head off such a confrontation, Mr Brown has let it be known he is planning a Cabinet reshuffle and the launch of a new raft of policies in early September.

Three members of the Cabinet came out in support of Mr Brown's leadership this weekend. Alistair Darling, the Chancellor, Harriet Harman, the Labour deputy leader, and John Denham, the universities secretary - on Sunday gave public backing to Mr Brown as the man to lead Labour into the next election.

"We need to be careful in the way we make our argument that we don't do things that inadvertently stop there being a good platform for Labour's case to come across," Mr Denham said.

Jon Cruddas, a backbencher and potential left-wing contender for the leadership, also tacitly criticised Mr Miliband over his actions last week.

In a newspaper article, Mr Cruddas accused "senior members of the party" of "a narcisstic dash for personal glory."

A Daily Telegraph poll last week showed that Mr Blair is the only major Labour figure who could significantly cut the Conservatives' lead.

With Mr Blair now out of parliament, Mr Miliband effectively declared himself the Blairite candidate to replace Mr Brown. He used a newspaper article to set out his own manifesto for Labour and then repeatedly refused to rule out a challenge for the top job.

The Foreign Secretary, 43, is a former adviser to Mr Blair and remains in regular contact with his former boss. Mr Blair is understood to have hoped that Mr Miliband would stand against Mr Brown last year when he vacated the Labour leadership.

Downing Street was silent on Mr Blair's memo, but some Brownites are privately furious at what they see as Blairite "disloyalty." Ed Miliband, the Cabinet Office minister and a leading Brownite, has even let it be known he will back the Prime Minister before the Foreign Secretary, his brother.

It was also confirmed today by the Downing Street spokesman that the Chancellor, Alistair Darling, has taken over responsibility for co-ordinating Government activity in London this week while Mr Brown continues his family holiday in Southwold, Suffolk.

Mr Darling replaces Harriet Harman, the Labour deputy leader, who was "minding the shop" last week. However, the spokesman emphasised, Mr Brown continues to remain "closely involved" in running the country.